Flash lamp system



Dec. 6, 1960 INPUT SE T LINE E. J. SMURA ET AL FLASH LAMP SYSTEM FiledSept. 9, 1957 lNVENTORS EDWIN J. SMURA RICHARD J. CARNEVALE UnitedStates Patent FLASH LAMP SYSTEM Edwin J. Smura, Apalachin, and RichardJ. Carnevale,

Endicott, N.Y., assignors to International Business MachinesCorporation, New York, N.Y., a corporation of New York Filed Sept. 9,1957, Ser. No. 682,773

8 Claims. (Cl. 315-241) This invention is related to a flash lamp systemand more particularly to a circuit for controlling the flashing of thelamp.

Flash lamps have found many uses in present day computer systems and thepresent invention has particular application in a computer system whichemploys a cathode ray tube printer to record the output. As is wellknown, the output information from the computer is displayed on thescreen of a cathode ray tube and then recorded on film through suitablephotographic means. In such a system it is oftentimes desired to recordat selected places on the film a form or page outline within which theinformation from the computer will be positioned. The form outline isgenerally recorded by means of a flash lamp which is fired under controlof a signal from the computer and in the past if the signal should failto fire the lamp for some reason, such as aging or overheating of thebulb, the computer would be immediately locked up.

A bulb may miss one flash in a 100,000 tries but this does notnecessarily mean that the bulb should be replaced or that it will not becapable of another 100,000 flashes and it would be preferred not to lockthe computer when the lamp fails to flash but rather to attempt to firethe lamp a second or third time if necessary.

Accordingly, the main object of the present invention is to provide acontrol circuit operative to fire a flash lamp, said circuit includingmeans for automatically efiecting a repeat operation whenever the lampfails to fire.

A further object of the present invention is to provide a startercircuit for firing a flash lamp in response to a computer signal andmeans included in said circuit for sending a recognition signal back tothe computer in response to the firing of the lamp.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawing,which discloses, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

A diagrammatic illustration of the invention is shown in theaccompanying drawing and viewed broadly, the present invention providesa relay operated pulse transformer circuit for initiating lamp startingand a resistance capacitance coupled cathode follower circuit forcontrolling repetitive lamp starting operations.

In the operation of the circuit, a positive input signal (-30 to +10volts, for example) from a computer or other suitable source is appliedto terminal 10 to raise the potential of control grid 11 and switch tubeT1 to a conducting state. Connected to the output of tube T1 is a relayR1 which is energized to close the contacts Rla and Rlb. In parallelwith the contacts Rla is a capacitor 12 connected between ground and asource of 300 volts so that it is normally charged to 300 volts andclosure of the Rla contacts will cause the capacitor 12 to dischargeinto the primary winding 13 of a pulse transoperation.

former 14. As a result, a very high potential is induced across thesecondary winding 15 of the transformer which initiates the starting ofa flash lamp L. A capacitor 16 in parallel with the lamp L and connectedbetween ground and a source of 800 volts will now discharge into thelamp causing a high intensity flash. With current flowing in the lamp aresistor 17 in series with the lamp generates a recognition signal whichmay be sent back to the computer via terminal 18 indicating that thelamp has flashed and instructing the computer to pull the input signalsupplied to the terminal 10 down to --30 volts. For example, aconventional trigger T in the computer may be provided, the output ofwhich normally places the input terminal 10 of the lamp circuit at anegative 30 volt potential. A suitable pulse on the set line will switchthe trigger to effect a rise in potential to positive 10 volts at theterminal 10 causing the flash lamp circuit to operate. A resultingrecognition signal developed iacross resistor 17 may be sent via theterminal 18 to a suitable amplifier A, the output of which is connectedto the reset line of the trigger T. Accordingly, the trigger will beswitched back to its normal state, indicating that the lamp has flashed,and the potential at terminal 10 will drop back down to negative 30volts to render the lamp circuit inoperative. If the lamp had failed toflash, a signal would not have been developed across resistor 17 and thetrigger will remain set keeping the potential at terminal 10 up to causea repeat operation of the lamp circuit.

Along with the closing of contacts Rla contacts Rlb also close and acapacitor 19 in parallel with the contacts R11) and connected betweenground and the 300 volt source is discharged thereby lowering thepotential at the point 20. Connected between the point 20 and thecontrol grid 21 of a cathode follower 22 are normally conducting neontubes 23 which are extinguished upon the discharge of capacitor 19resulting in a lowering of the potential on the control grid 21. Theoutput of the cathode follower is connected to the screen grid 24 of thetube T1 and the lowering of potential on the grid 21 reduces the cathodefollower output sutficiently to drive the screen grid 24 below cutoffand turn tube T1 011. As a result, the relay R1 drops out opening thecontacts Rla and Rlb.

Capacitor 19 is such that it takes approximately milliseconds after thecontacts Rlb open for the capacitor to charge back up to 300 volts afterwhich time the output of cathode follower 22 is raised thus raising thepotential at the screen grid 24 and conditioning tube T1 for operationagain. During this time the capacitors 12 and is also recharge toprepare the circuit for service again. The delay of 100 milliseconds isprovided to keep the number of flashes per second to 10 so as not toexceed the rating of power on the fiash lamp.

If the lamp should fail to flash, as is the case at times due to bulbaging or bulb heating, there will not be a recognition signal availableat the terminal 18 for transmission back to the computer and as a resultthe signal at terminal 10 will not be pulled down but will remain at +10volts. After the 100 millisecond delay, relay R1 is again energized andthe circuit will repeat As was previously mentioned, the repetitivefeature of the circuit is very desirable because it lengthens the usefullife of the lamp and the absence of the flash does not lock up thecomputer as is the case with a one and only one shot system.

In the preferred embodiment of the invention the pulse transformer isfed from a relay circuit rather than the customary thyratron discharge.The relay allows the pulse transformer to ring at its natural frequencythus giving several pulses and insuring greater reliability in firing ofthe lamp.

While there have been. shown and described and pointed outthefundamentalnovel features of the invention as applied to a preferredembodiment, it willbe understoodv that various :omissions andsubstitutions and changes in theform and details of. the deviceillustrated and its operation may be made by those skilled in the art,without departing from the spirit of the invention. It is the intention,therefore, to be limitedonly as indicated by the scope of the followingclaims.

What isclaimed is:

1. In an illuminating apparatus employing aflash lamp, a starter circuitresponsive to an input signal meansto supply above normal voltage tosaid lamp to cause same to flash momentarily, means associated with saidlamp for generating an output signal upon flashing of the lamp, meansresponsive to said outputsignal for controlling said input signal meansto render said starter circuit inoperable, and a control circuitresponsive to said input signal means and including means for effectingrepetitive operation of said starter circuit only in the event said lampfails to flash, said repetitive operation continuing until said lampflashes.

2. In an illuminating apparatus employing a flash lamp, an electrondischarge device responsive to an input signal, a starter circuitresponsive'to the output of said discharge device to supply above normalvoltage to said lamp to cause same to flash momentarily, meansassociated with said lamp for generating an output signal forcontrolling the termination of said input signal upon flashing of thelamp, and a control circuit responsive to the output of said dischargedevice and including means for conditioning said discharge device toeffect repetitiive operation of said starter circuit upon the absence ofsaid output signal.

3. In an illum nating apparatus employing a flash lamp, an electrondischarge device responsive to an input signal, a starter circuitresponsive to the output of said discharge device to supplv above normalvoltage to said lamp to cause same to flash-momentarily, meansassociated with said lamp for generating an output signal forcontrolling the termination of said input signal upon flashing of thelamp, and a control circuit responsive to the output of said dischargedevice and including means for switching said discharge device from anoperative state to an inoperative state, and time delay means forconditioning said discharge device for repeat operation to effectrepetitive operationof said starter circuit upon the absence of saidoutput signal.

4. In an illuminating apparatus employing a flash lamp, an electrondischarge device responsive to an input signal, a starter circuitresponsive to the output of said discharge device to supply above normalvoltage to said lamp to cause same to flash momentarily, meansassociated with said lamp-for generating an output signal forcontrolling the termination of said input signal upon flashing of thelamp, a cathode follower for controlling the operation of said dischargedevice, a capacitor for controlling the operation of said cathodefollower, means for charging said capacitor, and switching meanscontrolled by the output of said discharge device for vdischarging saidcapacitor to efiect the switching of said discharge device from anoperative state to an inoperative state, said switching means beingeffective when said discharge device is in an inoperative state to allowsaid capacitor to become charged whereby said cathode follower'willcondition said discharge device for repeat operation to effectrepetitive operation of said starter circuit upon the absence of saidoutput signal.

5. In an illuminating apparatus employing a flash lamp, anelectrondischarge device responsive to an input signal, switching meansresponsive to the output of said discharge device, a starter circuitcalled into operation by said switching means upon operation of saiddischarge device to supplyabovemormal voltageuto said lamp to cause sameto flash momentarily, a control circuit called into operation by saidswitching .meansupon operation of sa d discharge device to return saiddischarge-device to an inoperative state, said control circuit includingtime delay means operating under control of said switching means whensaid discharge device is in an inoperative state to conditionsaidtdischarget device for repeat operation.

6. In an illuminating apparatus employing a flash lamp, an electrondischarge device responsive to an input signal, a relay in the outputcircuit of said,..discha rge device, a starter circuit comprising acapacitor andipulse transformer for supplying above normal voltagetos'aid lamp to cause same to flash vmomentarily,.contacts of said relayin said starter circuit for calling sameinto operation in response tooperation of said discharge device, a control circuit for switching saiddischarge device from an operative state to an inoperative state, andcontacts of said relay in said control circuit for calling same intooperation in response to operation of said discharge device.

7. In an illuminating apparatus employing-a flash lamp, an electrondischarge device responsive to an input signal, a relay in the outputcircuit of saidtdischarge device, a starter circuit for supplying abovenormal voltage to said lamp to cause sameto flash momentarily, contactsof said relay in said starter circuit for calling same into operation inresponse to operation of said discharge device, a control circuitcomprising a cathodefollower having its output connected to saiddischarge device .to control the operation of same, a capacitor.discharge circuit for controlling operation of said cathode follower,means for charging said capacitor, and other contacts of said relayincluded in said discharge circuit for discharging said capacitor toefl'ect the switching of said discharge device from an operative stateto an inoperative state, said other contacts being effective when saiddis charge device is in an inoperative state to allow said capacitor tobecome charged whereby said cathode follower will condition saiddischarge device for repeat operation.

.8. In an illuminating apparatus employing a flash lamp, .a startercircuit responsive to an input signal to supply above normal voltage tosaid lamp to causesame to flash momentarily, an electronic triggerdevice operable to provide said input signal, means associated with saidlamp for generating an output signal upon flashing of the lamp,amplifier means connecting said output signal to said trigger devicewhereby .said trigger switches to cause termination of said inputsignal, and a control circuit responsive to said input signal andincluding means for eflecting repetitive operation of said starterIcircuit upon the absence of said output signal.

References. Cited in the file of, this patent UNITED STATES PATENTS2,342,257 Edgerton Feb. 22, 1944 2,426,602 Edgerton Sept.'2, 19472,478,908 .Edgerton Aug. '16, 1949

